Vehicle bodies and components are conveyed by a conveyor device in an automotive vehicle production line. Ordinarily, an overhead conveyor from which an upper part of a hanger suspends is preferably used in the conveyor device, as taught in Japanese Patent Application Laying-Open Publication No. 2005-162445 (JP 2005-162445 A). The conveyor device will be described below with reference to FIGS. 9A and 9B hereof.
As shown in FIGS. 9A and 9B, a plurality of hangers 102 is suspended on a support rail 101. Drive chains 104A, 104B, which have a plurality of engaging protrusions 103, are provided along the support rail 101.
For example, a front door 106 and a rear door 107 are suspended from a hanger 102. When the drive chains 104A, 104B are caused to rotate in the counterclockwise direction as shown by the arrows, the engaging protrusions 103 will engage with the hanger 102, and the hanger 102 will be conveyed. The plurality of hangers 102 will be conveyed in unison.
Transfer means 108 is provided between the drive chain 104A and the drive chain 104B. The hanger 102 is transferred from the drive chain 104A to the drive chain 104B, as shown in FIG. 9B.
Each transfer means 108 normally has its own drive source (e.g., a cylinder unit), and the speed thereof is controlled to allow conveying to be performed at high or low speed, or halted.
However, the transfer means 108 is generally used to move the hangers 102 over a relatively short distance LL, as shown in the drawings.
The distance LL is designed to merely move the hangers, and is thus used inefficiently. Using this distance for an installation stage or the like is therefore preferred. However, the length provided by the distance LL is insufficient, and a greater length is required.
When a plurality of transfer means 108 of length LL is connected in series to increase their length, a plurality of drive sources will have to be synchronized so that adjacent hangers 102 do not collide, and the synchronization control becomes more complicated. In addition, operating costs increase because of the need to operate a plurality of drive sources.